1. Field of the Invention
The present invention relates to antimicrobially treated material containing silver-based antimicrobial agents having a coloring preventing function, in particular to plastic compositions and various products using thereof, external skin agents, wet tissues and paste-type cosmetics. Furthermore, the present invention relates to methods of preventing coloring of antimicrobially treated material which have a coloring preventing function and contain silver-based antimicrobial agents.
In more detail, the present invention relates to products such as containers and packaging materials made with antimicrobial plastic compositions which have a coloring preventing function and comprise silver-based antimicrobial agents, bases of nucleic acid components, thiabendazole, and the like.
Further, the present invention relates to external skin agents and sheet-like cosmetics having a coloring preventing function which comprise silver-based antimicrobial agents and at least one or more kinds of components selected from purine bases, free bases thereof and thiabendazole.
2. Description of the Related Art
The antimicrobial effect of silver zeolite has been known for a long time (Patent No. 128654: “A method of producing hard water softening agent having an antimicrobial activity” filed by the Taiwan Institute of Invention in Aug. 12, 1937). Admixing of silver-based antimicrobial agents with various products and treatment of various products with silver-based antimicrobial agents have been generally practiced.
As the demand for silver-based antimicrobial agents expands, the silver-based antimicrobial agents have been actively developed, and a number of technical reports related to the production and use of such antimicrobial agents have been published (Japanese Patent Application Laid-open No. 1984-133235; Japanese Patent Application Laid-open No. 1985-100504).
Although silver-based antimicrobial agents are useful antimicrobial agents, a problem that products are undesirably colored upon application of these silver-based antimicrobial agents is getting a great deal of attention. Accordingly, technology for preventing coloring of products, in which the silver-based antimicrobial agents is used, is now under study. For example, a method for partially exchanging zeolite with ammonium ions has been proposed (Japanese Patent Application Laid-open No. 1988-265958; Japanese Patent Application Laid-open No. 1989-24860).
However, when silver-based antimicrobial agents are admixed with plastics or the like using such technology, the content of containers is occasionally colored due to the effect of silver ions although coloring of the plastics can be prevented to some extent. Furthermore, residual coloring and color development are big problems when an aqueous medium containing silver-based antimicrobial agents is retained in a carrier and used for wiping or when cosmetics containing silver-based antimicrobial agents are directly applied to the skin. For example, when an aqueous medium containing silver-based antimicrobial agents was retained in sheet bases such as paper or nonwoven cloth, the silver-based antimicrobial agents remaining after use adhered to the skin, clothes or the like and colored yellow to brown, which was hard to prevent.
Further, residual coloring and color development caused a problem even when silver zeolite antimicrobial agents were directly added to cosmetics or directly admixed with sheet bases without using an aqueous medium.
Characteristically, silver-based antimicrobial agents have a broad antimicrobial histograph to bacteria and fungi, are effective to various kinds of bacteria, are safe to a human body, do not generate resistant microorganisms, and are safe in terms of environmental pollution. Accordingly, their use in wet products, such as external skin agents and sheet-like cosmetics, and paste-type products used, for example, in caring babies, seniors or the like and in cosmetics are expected. However, in actuality, the coloring problem has been a bottleneck in use in products that have direct contact with the skin, such as cosmetics, since silver-based antimicrobial agents undesirably color the skin and clothes brown or yellow due to residual coloring or coloring of the silver-based antimicrobial agents themselves, as mentioned above.
In the field of cosmetics, silver-based antimicrobial agents have an excellent effect in preventing underarm and body odor, are also effective against acne bacteria, and can be used safely on the body. In particular, their use in wet tissues and paste-type cosmetics, such as deodorants, is promising. Useful pocket products are also expected.
However, as mentioned above, silver-based antimicrobial agents cause a serious coloring problem when cosmetic sheet-like wet products are made by soaking nonwoven cloth with an admixture of silver-based antimicrobial agents and an aqueous medium. Accordingly, methods of using silver zeolite antimicrobial agents in cosmetic products without undesired coloring have been in demand.
The present inventors directed their attention to the fact that while silver ions dissociated in water exhibit a remarkable antimicrobial effect when silver-based antimicrobial agents are placed under moist conditions, the silver ions are associated or oxidized to color yellow to brown, that the extent of such coloring depends on the amount of silver ions present in the water system, and that the amount of silver ions dissociated and released from the silver-based antimicrobial agents in the water system greatly changes under the influence of ions of salts and the like present in the water system.
The present inventors tried to solve the problem caused by using silver-based antimicrobial agents in producing cosmetics without undesired coloring when the silver-based antimicrobial agents are admixed with an aqueous medium to produce products such as external skin agents. As a result, it was revealed that when silver-based antimicrobial agents were admixed with external skin agents in cosmetics or the like, the degree of coloring by silver ions dissociated from the silver-based antimicrobial agents is greatly affected by the admixed components or air contained in the admixture so that the amount of silver ions dissociated and released from the silver-based antimicrobial agents in the water system had to be controlled in order to prevent the coloring since the prevention was occasionally difficult.
It was also revealed that when silver zeolite antimicrobial agents were admixed with sheet-like cosmetics, the coloring by silver ions was greatly affected by cosmetic components, components of nonwoven cloth used as a sheet base or air contained so that the amount of silver ions dissociated and released from the silver zeolite antimicrobial agents in the water system had to be controlled in order to prevent the coloring since the prevention was difficult and the influence of the silver ions was greater than that of the cosmetic components.
Accordingly, the present inventors tried to solve the problem caused by using silver zeolite antimicrobial agents in producing cosmetic sheet-like wet products without undesired coloring when the silver zeolite antimicrobial agents are admixed with an aqueous medium and nonwoven cloth was soaked in the admixture.
On the other hand, Japanese Patent Application Laid-open No. 1989-164722 proposes compositions as means for preventing coloring caused by silver, in which a UV absorbent is added to silver zeolite. However, no coloring prevention effect in containers and packaging materials could be attained since the coloring is caused also by the action of liquid components in the containers other than UV light. Japanese Patent Application Laid-open No. 1988-265958 and Japanese Patent Application Laid-open No. 1989-24860 propose antimicrobial resin compositions having a coloring prevention function in which exchangeable ions are partly or totally substituted with ammonium ions and silver ions. However, the color prevention effect is insufficient and in particular, containers for aqueous fluids are markedly colored. In Japanese Patent Application Laid-open No. 1991-145410, coloring by UV rays is prevented by incorporating amine silver complex ion into zeolite soaked in an ammonium ion solution.
Silver-related coloring is occasionally caused by a reaction of liquid components in containers other than light and no effective means is so far available to prevent such coloring. For example, Japanese Patent Application Laid-open No. 1991-181538 proposes compositions effective to weather-resistant coloring, in which silver zeolite, a hindered amine compound and a neutralizing agent are incorporated into a polyolefin resin containing a chlorine compound. According to this proposal, polymethylpropyl-3-oxy[4-tetramethylpiperidyl]siloxan is preferable as a hindered amine compound. However, coloring of containers and packaging materials caused by liquid contents was not sufficiently prevented using such compounds.
Conventionally, in antimicrobial plastic packaging products containing silver-based antimicrobial agents, particularly in plastic containers and packaging materials used for cosmetic products containing liquid components as the contents, coloring caused by a reaction between the liquid contents and silver ions incorporated into the packaging containers could not be prevented and thus it was difficult to contain aqueous substances such as cosmetic lotions in containers which contain silver-based antimicrobial agents.